Krell Restoration

Hi Dderham1948 - I just saw your post. Just a few additional comments.

When you say "its been 15 years of hard use" it tells a lot.

Whether it goes back to Krell direct or not, may be dependent on the weight / distance / logistics. There is a crossover point when weight and distance can rule out sending to the manufacturer. In my case almost 200 lbs. I had no choice. A few friends and I are lucky as there is a certified past Krell tech in the Ontario L5B XXX postal code. This person has even worked on the $150K Krell Master Reference Amplifier. So when using local techs credentials are very important.

BTW - I could not confirm from your post.
When you say 802s do you mean two (plural) B&W matrix series or other series of B&W 802's ?

The FPB series has real synergy with the 800 series matrix line. My generation krell 600 was chosen due to the synergy with my reference matrix 800 speakers. The same ones used by Dan D'Agostino when his main system was FPB series with matrix 800. He liked the 800 series matrix line so much that he designed his own Krell built to B&W spec Bass Alignment Filters.

I just got off the phone with Dan recently and he gave me some more tweaks for my system if I ever get tired of listening to music. :^)
Very open and easy to talk with. I encourage you to call him at 480-575-3069 in Arizona. He may know someone qualified in your own backyard if sending the amp back to Patrick at Krell becomes a no go.

Cheers and Good Luck.

Dderham1948
Ct0517. Front of Matrix woofer is partially separated from the speaker. May only need to be glued, don't know yet.
Anyone know of a hidden stash of Matrix drivers?

Dderham1948 - this site lists parts and prices.

B&W Parts and Pricing

You can type in your model and series and it lets you know the availability of parts and their prices. They are showing out of stock on your woofers.
This is not a problem. Your woofer can be brought to any reputable speaker rehab shop in your area and repaired as new.

Loosen the bolts on the woofer slowly. When all are starting to move (not seized) cradle the bottom of the woofer and start taking the bolts out. The woofer will want to fall out from bottom toward you so cradle it. Once bolts are out the woofer may be stuck to the cabinet if its never been out. Slowly pry away with a pick. When it gives it will be all at once so keep cradling it. I put two small pieces of green painters tape on cabinet just above the woofer showing which wires blue / brown go where. For when you put it back. Bring woofer to the shop. They will repair it and inspect the spider for flabbiness. If it need replacing do all woofers same time. You will be back in business.

Your Krell preamp is not like the Amp. It doesn't go through the stress cycles of high heat/ cool down. I would have it inspected at same time. Its not a given that all capacitors wear out over XX years on a preamp. i.e. My Studer tape failed. My tech thought for sure it needed new power supply capacitors. When checked they were at new condition specs still. (knock on wood :^) .
It turned out to be another problem. let us know how u make out.

Cheers

Audiolabyrinth
can you share some of the tweak's Dan D Agostino shared with you, I have talked to him myself on the phone over the last few month's, do tell please.

Hi Audiolabyrinth

Sure, but first let me preface this. In all my conversations with amplifier (power) guys there has always been a common theme in the talks. They all want to discuss power and how to control more with the speakers. Whether they are trying to do this with as little power as possible, or with as much as can be made. Both extremes. You know what they say - power corrupts, absolute power corrupts absolutely. :^)

The tweaks Dan discussed revolved around his setup of his then Matrix 800 speaker system. How best to say this. These speakers are like zombies on steroids, a freak of nature kind of speaker system. A one time only offering from B&W under John Bowers regime - the (B) in B&W.

Dan talked about this total end user control of the speakers. The matrix 800 can be a sort of speaker brothel in this way. Let me explain. The driver system in each matrix 800 speaker (two woofer cabinets, 2 mids, 1 tweeter) are isolated in their own cabinets with their own easy to get at crossover. Unbolt the back plates - there are the crossovers for each driver. Naked and open access. You don't even need your wifes help to lay the speakers on their side or upside down. There are the crossovers staring at you in the face. These days some manufacturers epoxy up these areas so not to tamper with them. What were the British thinking. Very dangerous for a curious audiophile. Which is why for me in my current "music lover" happily listening to music phase, these easy to access speaker guts pose no threat. Sorry for digressing....

So four separate external crossovers per speaker allows for quad wiring (which I am doing), and bi, tri and quad amping if you really want to go crazy.
I am also using Dan's Krell Bass Alignment filters which I preferred to two other 3rd party ones I have used.

He discussed bringing in as many
Krell Crossovers as needed to do this bi, tri, quad amping and bypassing the internal crossovers.

Here is a

Pass Labs version as well for comparison.

With the above you can control the volume coming out of each driver separately. You can therefore based on your own ears and your room, make the speaker highly resolving, or sweet and warm. Switch back and forth with different genres maybe. Go crazy. It allows for dialing in your preferences with fewer room treatments, and a little lesser placement worries. This sounds all good especially if its a shared room with your wife. But .....she would probably never allow these matrix 800 in the house to begin with.
Now a problem I see is you are going from the matrix 800's unique high quality passive crossovers, to a much more complicated quality multi active crossover/s system. I've heard others say transparency takes a hit. I don't know the answer to this. It probably becomes a YMMV type of thing. You need to hear it in your own room.

As it is I have a dedicated space and these room friendly monsters were very easy to dial in. At 93db 4 ohm design the Krell 600 amp is barely cruising even on the high spls.

Cheers

Hey John.
I got curious upon first getting it. But due to the weight, and lack of help I had my local tech near me check it out. He gave it a clean bill of health so it was good to try out. It replaced 200 wpc monoblock OTL's. I had planned to use it for a period, and if I liked it to have it overhauled for the long run. The honeymoon with it became extended and its prime winter time listening for me right now. The Tech mentioned on this thread ended up with my other amp instead. Sorry for the confusion. When that amp returns from him, and good outside weather also returns, I will again attempt to bring it (with help) down to him to do his work on it. As mentioned here one of the speakers Dan D'A'gostino designed it around was the B&W 800 Matrix series. So I don't want to mess with synergies in play. Hearing is believing. The tech will therefore keep the design intact and change out capacitors and whatever else he feels will benefit.

An observation on running it and I would be interested in others experiences.
When I listen with digital it gets kind of warm only. Digital has a loudness factor. When I get serious and crank it with a low level vinyl signal it gets hot, but not so hot that I cannot keep my hand on it. I believe how hot it can get is based on the source type (digital versus vinyl), your listening habits, the speakers you use, and most important, the room volume in play. I haven't tried it yet, but I am pretty sure if I was using it with less friendly speakers like my Acoustat ESL's at 81db sensitivity and their 40 ohm bass requirements, versus the 800's 93db sensitivity and 4 ohms it would get much much hotter. So if anyone is looking at buying one of these Krell's I would be trying if possible to find out about the above factors. Gives you an indicator of how hard it was run.

Also. We always hear about doubling down for Solid State - well what about halving up above the 8 ohms ? If my amp does 600 wpc at 8 ohms and 2400 wpc at 2 ohms that's all fine and good. But how much power does it make at 32 or 64 ohms that Acoustat speakers need for the bass (which sucks the most power). Does the power curve go the other way, halving up based on 16, 32 ohms ? So at 16 ohms it would make half at 300 wpc, and again 150wpc at 32 ohms. I don't know the answer. Would have been a good question for Dan D'Agostino. I know the Acoustat are 40 ohms and up for their bass because my previous OTL's were designed by their manufacturer around them, and for their requirements. We had many conversations about it.

Appreciate the comments Audiolabyrinth

I don't like open questions so I asked Patrick at Krell about the impedance load wpc power ratings above 8 ohms.

Hi Chris,
This is a question I do not get asked too often so I am not quite as knowledgeable in this area. I do know that if the load of the speaker goes up then indeed the power output of the amplifier does indeed go down so your figures below are accurate (in this case 600wpc @ 8, 300wpc @ 16 etc).
Hope this helps.
Patrick